How long does it take to break in a guitar pickup?
"Pickups can be broken in?" Yes.
There are a lot of guitar players out there who don't realize that the sound of a guitar pickup changes over time. Sometimes the change is good while other times it's bad.
I'll cover the bad first.
Bad break-in: High-output humbuckers
This happens mostly with, you guessed it, "metal" guitars.
High-output humbuckers do not break in well and never have. There are "metal" guitars aplenty out there with humbucker pickups that are useless after about 12 to 24 months, depending on how much the guitar was played.
The break-in period of a high-output humbucker is quick, and usually takes less than 6 months. After that, the pickup sounds perfect, but then starts to sound awful in another 6 to 12 months.
Specifically, what happens is that any treble response the pickup had is pretty much gone. The output decreases significantly, and the string output balance is all messed up because the 4, 5 and 6-string pole pieces are weaker than the 1, 2 and 3-string pole pieces (mainly due to power-chord-5th playing.)
However, there is a solution.
Take the above cheap guitar, install a proper pickup upgrade set that isn't "metal" but with plenty of balls, purposely use a standard gauge string set in 9-42, 10-46 or 11-52 size, and you'll get at least 3 solid years of play. Given the fact most "metal" guitars only last for about 2 years before they sound like total crap, that's pretty darned good.
Yes, the guitar has a thin U-shape neck, which metal players like. Buy it, upgrade the pickups and then beat the crap out of it, because that's what it's built for.
All your friends who overspent on their guitars will end up with awful-sounding pieces of junk in less than 2 years and probably still owe money on it because they financed the stupid thing. You, on the other hand, will have a guitar that was paid in full years ago, still plays great and still sounds great. That's money well spent.
Good break-in: Stratocaster (or Telecaster, Jazzmaster or Jaguar)
Proper-voiced Strat vs. every other Strat
An example of a proper-voiced Strat pickup is a brand new Mexico-made Fender Standard Stratocaster. That guitar has pickups that are labeled by Fender as "Standard Single-Coil Strat."
For other Strats both for Made-in-USA and Mexico, you will see some pickups labeled by Fender as "Custom Shop" this/that/the-other-thing. Some will be labeled as being "50s" sounding, some state "Vintage," some state "Hot," and so on.
The pickup that is the easiest to break in on the Strat is the Standard Single-Coil. It is a pickup that is predictable without any wacky voicing going on. In other words, a plain, honest-to-goodness Strat sound.
Are the Squier Strats the same way? For the most part, yes. Unless specifically stated otherwise, a Squier Strat is either stocked with plain Strat pickups or the Duncan Design, both of which break in easily just like the ones in the Mexico Strat do.
The main complaint about plain Strat pickups is that they don't have enough output, and/or that they're too "bright."
Concerning the output, the Strat single-coil by nature is low-output. As I've said many, many times, I can guarantee that you don't want a "hot" Strat. What you want is a cheap compressor pedal. Seriously, go get one. If you want your Strat to continue sounding like a Strat but with your notes heard better along with more prominent string ring, get the damned compressor.
As for the over-bright thing, that happens because the pickup is new. Strats with plain single-coil pickups that haven't been played before will always have a ton of treble to them. The cure for this? Play the thing.
How long will it take until a Strat's pickups are broken in?
Strats use "hard" pickup magnets that take longer to break in. I can personally begin to break in a Strat's pickups - assuming they're stock single-coils - in about 3 months because I will play the crap out of that thing. Note that I said begin to break in, meaning not fully broken-in.
As far as when I can fully break in a set of Strat pickups, that takes me about 6 to 8 months.
For other players that don't play as often, it can take up to a year.
What happens when the pickups are broken in on a Strat?
Over time as you play the guitar, certain pole pieces will have more vibration put over them compared others. Which poles, specifically? That all depends on how you play and what type of strings you use. Maybe you pick near the bridge. Maybe you pick in the middle. Maybe towards the neck. Maybe you use nickel-plated steel strings. Maybe you use "pure nickel" strings. Heck, maybe you use flatwound strings. All those things and more contribute to how a pickup breaks in.
What you're doing each time you play is "conditioning" those pole pieces to react a specific way when you play.
Do you have to play a specific way to break in pickups? Nope. Just play as you normally do.
You will know your Strat's pickups are broken in when you pick up the guitar one day, plug in, tune up, strike a chord and whoa... there it is... "that sound." You will ring out a chord and the guitar just sounds beautiful. And it will continue to sound beautiful for a good long time because now that Strat is, in a word, yours.
"I've never had that moment with my Strat."
If you've had your Strat over a year and have been playing it regularly but "that moment" hasn't happened, the reason why is probably because you've never been totally comfortable with the guitar. If you're not comfortable with it, you will never have that "that moment," and it's time to try a different guitar that's not a Strat.
Remember, Strats aren't for everyone.
Good break-in: Les Paul (or SG, Explorer, Flying V)
Like with the Strat, the best pickups for easy break-in that Les Pauls use are the plain kind without any special voicing. The Epiphone Les Paul Standard for example uses what are called AlNiCo Classic Humbuckers, and those are a-okay.
The break-in time for a plain humbucker is quicker compared to the plain Strat single-coil as it typically uses "soft" magnets. Complete break-in can happen in under 6 months with regular play.
However, there are a few things about the dual coil Les Paul pickup that are distinctively different compared to a Strat single-coil that affects break-in time.
1. Adjustable outer-coil pole pieces
Many Les Paul models by both Gibson and Epiphone allow individual pole piece height adjustment on the outer coils. Most players keep these screwed down flat, but you have the option of raising or lowering them depending on your string volume preference, and this does affect how the pickup breaks in over time.
If for example you raise the poles on strings 1, 2, 3 and 4 on the front (neck) pickup and leave it that way because you like more output on the unwound strings when soloing, you would probably hear a significant difference in sound if you lowered them after playing the guitar for a year.
If you want to play it safe, so to speak, leave the poles screwed down for a while until you've played the guitar for a few months. Let the magnets "get used" to the way you play and for what strings you use, then adjust later.
Also know that this is not the same as adjusting overall pickup height. When you raise/lower pole pieces, you're doing that to specifically adjust individual string volume and not the whole pickup itself. It is normal to raise/lower the entire pickup to your preference, but for individual poles, I would personally wait until playing the guitar for a few months before adjusting those.
2. Wound strings (usually) always ring louder on the dual coil
On Strats, the non-adjustable pole pieces are either set up to follow the curve of the fretboard, or use a vintage staggered pattern where the G string pole is the highest. In either pattern, the unwound strings are almost always the loudest when playing.
On the Gibson/Epiphone humbucker, the the exact opposite is true and the wound strings are the loudest because the poles are set flat (as in thicker string = louder vibration = wound strings heard loudest because poles are flat.)
All you need to know here is that on a brand new set of plain humbuckers, the wound strings will by nature ring out louder. Give it time, play the guitar regularly, and the sound will even out as you break in the pickups.
3. Too much "honk" when both pickups used
Brand new plain humbuckers in a Les Paul usually result in a very "honky" sound when both pickups are used at the same time. This is because the pickups are brand new and have some trebly "bite" to them.
Again, give it time, play the thing, break in the pickups and the sound will even out.
There is however a quicker right-now solution even on new Les Pauls. Because the volume controls are 500K linear taper potentiometers, you can roll the rear (bridge) volume control from 10 to 9 or 8 and that will cut out just enough treble so the both-pickup setting sounds better until the pickups are broken in later on.
And no, this doesn't work on Strats because it uses an audio taper potentiometer for a master volume control. Linear taper gives you quick-access treble cutoff with a slight turn of the knob, but audio taper does not. On the Strat, use the tone controls instead.
"The tone control doesn't work for the bridge pickup on my Strat."
The traditional Stratocaster wiring setup has no tone control wired to the bridge-only pickup selector setting. Take it to a guitar tech to wire it in. Or wire it in yourself. It takes about 10 minutes to do and all you need is a 2-inch piece of wire.
Does breaking in pickups make a bad-sounding guitar sound good?
No, it doesn't.
If a new guitar you try out sounds bad to your ears from the start, then it sounds bad, and no amount of break-in time will fix that.
If on the other hand a new guitar "sounds generic," meaning a sound that's neither bad nor good, that's a guitar where break-in can make it sound better over time.
Every new Strat and Les Paul with regular, non-vintage-voiced, non-wacky-output-voiced pickups will sound generic. They will sound like every other generic Strat and Paul you've ever heard. Is this normal? Yes.
It is also normal that break-in time is required before the guitar really starts to sound good. And no matter what anyone says, there is no way to break in a guitar quickly.
Break-in requires you actually playing the guitar for a while, and the amount of break-in time depends how much you play the guitar. Since I play often, I can fully break in pickups in about 8 months. For others it takes a year or maybe slightly longer.
On a final note, the absolute fastest way to break in a guitar is to gig with it. If you gig regularly, any new guitar you take on stage should have fully-broken-in pickups in less than 6 months.